Plasma chambers are often used to generate a plasma. Ions from this plasma are then extracted from the plasma chamber through an aperture to form an ion beam. This plasma may be generated in various ways. In one embodiment, an antenna is disposed outside the plasma chamber, proximate to a dielectric window. The antenna is then excited using an RF power supply. The electromagnetic energy generated by the antenna then passes through the dielectric window to excite feed gas disposed within the plasma chamber.
The plasma that is generated is then extracted through an extraction aperture. In some embodiments, the extraction aperture may be rectangular or oval, where the length is much larger than the width of the opening. However, in these embodiments, the ion beam that is extracted from the plasma chamber may not be of the desired uniformity across the length of extraction aperture. For example, the plasma density may be greater near the center of the plasma chamber and may be reduced in regions away from the center.
This plasma non-uniformity may affect the extracted ion beam. For example, rather than extracting an ion beam having a constant ion density across its width, the ion beam may have a greater concentration of ions in a first portion, such as near the center, than in a second portion, such as at its ends. In other embodiments, it may be desirable to create an ion beam having a known non-uniformity.
Therefore, it would be beneficial if there were an improved system for extracting an ion beam from a plasma chamber. More particularly, it would be advantageous to more finely control the uniformity of a ribbon ion beam that is being extracted from a plasma chamber.